This invention relates to improvements in means and methods for mounting and tuning a whip type antenna in connection with a mobile, high frequency transceiver.
The typical whip type antenna comprises a length of stiff wire or rod mounted to project upwardly and outwardly from the vehicle in which the related transceiver is employed. A conventional installation of such an antenna normally requires the formation of apertures in or other defacement of the vehicle to which it mounts and/or the application of special fasteners. The fasteners employed are oftentimes in locations which make them difficult to manipulate, correspondingly making the antenna difficult to install.
A whip type antenna may embody a loading coil which is electrically attached, either intermediate the length thereof or at its base. The function of this coil is to make the antenna seem longer to the coaxial cable connecting the antenna system to the transceiver, hopefully to thereby increase its efficiency. It has, in any case, been quite a problem to tune such an antenna, with or without the loading coil. Good tuning facility has been very difficult to achieve since the tuning requirements vary from vehicle to vehicle in which the antenna may be embodied and therefore cannot be preset. The normal method of tuning is to clip off short lengths of the antenna, after it is installed, until it appears that optimum performance of the system has been reached. The potential quality of performance of the antenna system is determined during the tuning procedure by applying an SWR meter to the coaxial cable which extends between the transceiver and the antenna. As must be readily acknowledged, this method of tuning antenna systems is awkward and time consuming. Since tuning is normally a matter of "cut and try", oftentimes too much of the antenna is cut off, in which event the antenna must be replaced.
To tune an antenna system one might in a case of a loaded type antenna try to vary the inductance of the loading coil. This, however, is mechanically difficult. One might also incorporate in the antenna system a series variable capacitor, which would act to cancel some of the inductance of the loading coil. This last has not been done because of the expense and the physical incompatability of a variable capacitor on the exterior of a vehicle.
It is to the elimination of the aforementioned tuning and mounting problems that the present invention is directed.